RADIO ASTRONOMY Journal of the Society of Amateur Radio Astronomers Mar-Apr 2021 - SARA Scope in a Box
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RADIO
ASTRONOMY
Journal of the Society of Amateur Radio Astronomers
Mar-Apr 2021
SARA Scope in a Box
1
Contents
Radio Waves ...................................................................................................................... 3
President’s Page ................................................................................................................ 3
Editor’s Notes .................................................................................................................... 4
Dennis Farr
News .................................................................................................................................. 5
SARA President
Technical Knowledge & Education: ................................................................................... 9
Richard A. Russel
Bogdan Vacaliuc Announcements ~ March-April 2021 .............................................................................. 11
Editors
For Your Radio Astronomy Bookshelf ............................................................................. 13
Steve Black
Whitham D. Reeve BAA Radio Astronomy Section 2021 JANUARY ............................................................... 14
Michael Stewart
Contributing Editors SuperSID .......................................................................................................................... 23
Radio Astronomy is published Feature Articles ............................................................................................................... 26
bimonthly as the official journal of
New Specialty Amplifier with Small Parabolic Antenna Advances Hydrogen Line
the Society of Amateur Radio
Astronomers. Duplication of Observing ........................................................................................................................ 26
uncopyrighted material for
educational purposes is permitted “Scope in a Box” First Experience and Some Enhancements. ......................................... 30
but credit shall be given to SARA and
to the specific author. Copyrighted
Sample of HF Radio Reflections from Aurora Observed at Anchorage, Alaska USA ....... 40
materials may not be copied without Getting the Best out of PRESTO(1) - Part 2 The PRESTO Period/P-Dot Search Graphic .. 44
written permission from the
copyright owner. Mapping Extent of Neutral Hydrogen Clouds near Sagittarius A* at 1420 MHz ............. 54
Radio Astronomy is available for RF Choke for VLF and LF Applications ............................................................................. 64
download only by SARA members
from the SARA web site and may not Superlatives in Science Journalism and other Science Junk compiled for April 1, 2021 . 73
be posted anywhere else.
Membership .................................................................................................................... 75
It is the mission of the Society of
Amateur Radio Astronomers (SARA) New Members ................................................................................................................. 75
to: Facilitate the flow of information
pertinent to the field of Radio
Journal Archives & Other Promotions ............................................................................. 76
Astronomy among our members;
SARA Online Discussion Group ........................................................................................ 76
Promote members to mentor
newcomers to our hobby and share What is Radio Astronomy? .............................................................................................. 77
the excitement of radio astronomy
with other interested persons and Administrative ................................................................................................................. 78
organizations; Promote individual
and multi station observing Officers, directors, and additional SARA contacts ........................................................... 78
programs; Encourage programs that
enhance the technical abilities of our Resources ........................................................................................................................ 79
members to monitor cosmic radio
signals, as well as to share and Great Projects to Get Started in Radio Astronomy ......................................................... 79
analyze such signals; Encourage
educational programs within SARA Radio Astronomy Online Resources ................................................................................ 81
and educational outreach initiatives.
For Sale, Trade and Wanted ............................................................................................ 83
Founded in 1981, the Society of
Amateur Radio Astronomers, Inc. is a SARA Advertisements ...................................................................................................... 85
membership supported, non-profit
[501(c) (3)], educational and SARA Brochure ................................................................................................................ 87
scientific corporation.
Copyright © 2019 by the Society of
Amateur Radio Astronomers, Inc. All
rights reserved.
Cover photo: Alberto Sagüés
2
Radio Waves
President’s Page
Just finished the Spring Conference. Great international attendance. As always,
the presentations were top notch. If you did not attend, you are missing one of
the greatest benefits of belonging to SARA.
We have once again decided to hold the Eastern conference as a virtual ZOOM
conference. We are very hopeful that 2022 will be the year we return to Green
Bank for an in-person conference. There will still be a virtual ZOOM conference.
Dates will be July 31 and August 1.
The scope in a box program is fully implemented. All we need now are orders. Remember, the kit could be made
available as a grant to worthy programs. If you know of a group that might qualify, please have them contact us
at grants@radio-astronomy.org
Please take a moment to check out the new online SARA store. It should be much easier now to order anything
we offer using one site for both PayPal and Credit card payments.
https://www.radio-astronomy.org/store/
The Drakes lounge monthly ZOOM meetings are extremely interesting and cover topics in an informal manner.
Typically, we are getting about 20 people attend. Always room for more. You should be receiving an email each
month with the schedule and link to the meeting. The meetings are held the 3rd Sunday of each month starting
at 1400 ET.
We have redone the membership brochure that is used as a handout at meetings and conventions such as
Hamvention. The new brochure can be seen at https://www.radio-astronomy.org/pdf/brochure.pdf or, click on
the link on the membership page. If anyone has any of the old brochures, please throw them away. They had
names and addresses on them that have changed.
Keep your antennas pointed up!
Dennis
3
Editor’s Notes
We are always looking for basic radio astronomy articles, radio astronomy tutorials, theoretical articles,
application and construction articles, news pertinent to radio astronomy, profiles and interviews with amateur
and professional radio astronomers, book reviews, puzzles (including word challenges, riddles, and crossword
puzzles), anecdotes, expository on “bad astronomy,” articles on radio astronomy observations, suggestions for
reprint of articles from past journals, book reviews and other publications, and announcements of radio
astronomy star parties, meetings, and outreach activities.
If you would like to write an article for Radio Astronomy, please follow the newly updated Author’s Guide on the
SARA web site:
http://www.radio-astronomy.org/publicat/RA-JSARA_Author’s_ Guide.pdf.
Let us know if you have questions; we are glad to assist authors with their articles and papers and will not hesitate
to work with you. You may contact your editors any time via email here: edit@radio-astronomy.org.
The editor(s) will acknowledge that they have received your submission within two days. If they do not reply,
assume they did not receive it and please try again.
Please consider submitting your radio astronomy observations for publication: any object, any wavelength.
Strip charts, spectrograms, magnetograms, meteor scatter records, space radar records, photographs;
examples of radio frequency interference (RFI) are also welcome.
Guidelines for submitting observations may be found here: http://www.radio-astronomy.org/publicat/RA-
JSARA_Observation_Submission_Guide.pdf
Tentative Radio Astronomy due dates and distribution schedule
Issue Articles Radio Waves Review Distribution
May – Jun June 12 June 20 June 25 June 30
Jul – Aug August 12 August 20 August 25 August 31
Sep – Oct October 12 October 20 October 25 October 31
Nov – Dec December 12 December 15 December 20 December 31
4
News
2021 SARA Annual Conference – Call for Nominations
As required by Section 3 of SARA By-Laws (see below), this is the official call for nominations for SARA officers and
board members. If you are interested in running for office and would like to know more about the positions, please
contact a board member or SARA President Dennis Farr. The requirement to be on the board is to attend the
board meetings at the annual meeting and to actively participate in board-related activities, usually email or
teleconference meetings. If you are unable to attend the annual meetings, then the director at large position may
be for you. This position is a full board position except that attending the annual meeting is not required. The
following positions will be up for election in Aug 2021: Secretary, Treasurer, two Directors at Large, and two
regular Directors.
If you would like to run for one of the available SARA officer or board positions, please send a note to Secretary
Bruce Randall, copying President Dennis Farr. The president and secretary will “nominate” qualified individuals
who volunteer. If you nominate someone, you must get their permission prior to nomination.
Contact information:
Secretary: Bruce Randall, NT4RT, https://www.radio-astronomy.org/contact/Secretary
+1 803-327-3325
President: Dennis Farr, WB4RJK, https://www.radio-astronomy.org/contact/President
+1 248-425-6016
Text from the By-Laws: SECTION 3:
Elections of Directors and Officers will be accomplished by the President placing an initial call for nominations in
"The Journal" no less than ninety (90) days prior to the regular scheduled meeting. Two (2) nominations from
different members will be required to nominate a member for an office. No less than thirty (30) days prior to this
meeting (in a newsletter issued prior to the meeting), the President will place a notice of the results of the
nominations in "The Journal", along with a ballot for the members to use to vote for the nominee of their choice.
This ballot will be forwarded to the Secretary for collection and counting at the regular meeting.
SARA Student & Teacher Grant Program
All, SARA has a grant program that is, sad to say very underutilized. We will provide kits or money to students and
teachers including college students to help them with a radio telescope project. SARA can supply any of the
following kits:
• SuperSID
• Scope in a Box
• IBT (Itty Bitty Telescope)
• Radio Jove kit
• Inspire
• Sky Scan
We can also provide up to five hundred dollars ($500.00 USD) for an approved radio telescope project.
5
We have on occasion provided more money based on the merits of the project and the SARA Grant Committee
approval.
More information on the grant program can be found at the URL below.
SARA Student and Teacher Project Grants | Society of Amateur Radio Astronomers (radio-astronomy.org)
All that is required is the SARA grant request form be filled out and sent in. If it needs more work for approval, we
will work with the student to help insure their success.
Please pass the word that SARA will fund any legitimate radio telescope project anywhere in the
world.
If you have a question, contact me at crowleytj at hotmail dot com
Tom Crowley
SARA Grant Program Administrator
Drake’s Lounge
Join the SARA community as we discuss the latest astronomy and radio astronomy news. The lounge also provides
a forum to share and get advice on your radio astronomy projects from very experienced amateur radio
astronomers.
Drake’s Lounge is every month on the 3rd Sunday at 2 pm Eastern time. ZOOM email notifications will be sent to
all members.
See you there!
2021 SARA Eastern Conference is Virtual Only Again
(Hopefully for the last time!)
We are sorry that we will not be able to see each other at Green Bank this year but we are planning to restart the
physical conferences next year at the VLA for the Western Conference and Green Bank for the Eastern Conference.
The 2021 SARA Eastern virtual conference will be held on Saturday and Sunday to allow for peoples work. The
new dates are July 31 – August 1, 2021. The schedule will include sessions all day Saturday and half of the day
Sunday afternoon to accommodate peoples worship services in the morning.
Conference cost will be $25 to cover expenses.
Register at: https://www.radio-astronomy.org/node/318
Contact Rich Russel (Conference Coordinator) if you would like to present a paper.
drrichrussel@netscape.net
6
SARA 2021 Eastern Conference Keynote Speaker
Dr. Sander Weinreb
Dr. Weinreb was awarded the 2008 Grote Reber Medal for lifetime innovative
contributions to radio astronomy. His pioneering developments of novel techniques and
instrumentation over nearly half a century helped to define modern radio astronomy.
http://www.weinreb.org/sandy/index.html
Presentation
New Directions in Radio Astronomy
In the past we believed that astronomical sources other than planets only varied over
times of millions of years. In the recent several years, a whole new world of sources with
variations in the time scales of milliseconds to months have become exciting targets for
new research. The most widely studied time-variable sources in radio astronomy are the
Fast Radio Bursts, FRBs – a ms pulse of radiation in the low microwave range which
sweeps in frequency and in most cases does not repeat. The search and characterization
for these single-event objects are tantalizing objectives for amateur radio astronomers.
This talk will begin with discussion of FRBs followed by descriptions of new radio
astronomy arrays, and new LNAs with noise of the order of 10K without a need for costly
cryogenic cooling.
7
Phys.org ~ Video: A signal from beyond: https://phys.org/news/2021-02-video.html
Spaceweather.com ~ Ham Radio Signals from Mars:
https://spaceweather.com/archive.php?view=1&day=17&month=02&year=2021
Hey, Mac, of course it has, but what’s up with the problng?: Phys.org ~ Has Earth been
visited by an alien spaceship? Harvard Professor Avi Loeb vs. everybody else:
https://phys.org/news/2021-02-earth-alien-spaceship-harvard-professor.html
Phys.org ~ Delayed radio flares from a tidal disruption event:
https://phys.org/news/2021-02-radio-flares-tidal-disruption-event.html
The SETI Project ~ Observatories: https://exoplanetschannel.wixsite.com/home/observatories-1
Universe Today ~ One Type of Fast Radio Bursts… Solved?:
https://www.universetoday.com/150293/one-type-of-fast-radio-bursts-solved/
American Geophysical Union (AGU) ~ A 21st Century View of the March 1989
Magnetic Storm: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019SW002278
CU Boulder Today ~ NASA-funded project to explore one-of-a-kind lunar observatory:
https://www.colorado.edu/today/2021/03/01/nasa-funded-project-explore-one-kind-lunar-observatory
Universe Today ~ NASA is Considering a Radio Telescope on the Far Side of the Moon:
https://www.universetoday.com/150417/nasa-is-considering-a-radio-telescope-on-
the-far-side-of-the-moon/
Thomas Ashcraft Radio Fireball Observatory ~ Meteor Fireballs in Light and Sound:
https://apod.nasa.gov/apod/ap210315.html
Phys.org ~ Cosmic lens reveals faint radio galaxy: https://phys.org/news/2021-03-
cosmic-lens-reveals-faint-radio.html
National Science Foundation ~ NSF begins planning for decommissioning of Arecibo
Observatory’s 305-meter telescope due to safety concerns:
https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674&org=NSF&from=news
Phys.org ~ Eight new millisecond pulsars discovered by MeerKAT:
https://phys.org/news/2021-03-millisecond-pulsars-meerkat.html
Universe Today ~ There Could be Magnetic Monopoles Trapped in the Earth's
Magnetosphere: https://www.universetoday.com/150603/there-could-be-magnetic-
monopoles-trapped-in-the-earths-magnetosphere/
Youtube Video ~ The discovery of pulsars - a graduate student's tale (Jocelyn Bell Burnell: “In this talk I will
describe how pulsars were accidentally discovered, and reflect on several instances where they were 'nearly'
discovered. I will highlight the implications for new telescopes with high data rates.”):
https://www.youtube.com/watch?v=ot1Ggv6YZyQ
8
ScienceNews ~ A new black hole image reveals the behemoth’s magnetic fields:
https://www.sciencenews.org/article/black-hole-picture-magnetic-fields-event-
horizon-telescope
YouTube video ~ Interview: Jack Burns and the Lunar FARSIDE (Radio) Telescope:
https://www.youtube.com/watch?v=Ubdzspuf2_Q
ScienceNews ~ The ‘USS Jellyfish’ emits strange radio waves from a distant galaxy
cluster: https://www.sciencenews.org/article/uss-jellyfish-galaxy-cluster-strange-
radio-waves
Phys.org ~ Radio telescope reveals thousands of star-forming galaxies in early Universe:
https://phys.org/news/2021-04-radio-telescope-reveals-thousands-star-forming.html
Research Notes of the AAS ~ The First Fast Radio Burst Detected with VLITE-Fast:
https://iopscience.iop.org/article/10.3847/2515-5172/abea22
History of Geo- and Space Sciences ~ The formation of ionospheric physics –
confluence of traditions and threads of continuity:
https://hgss.copernicus.org/articles/12/57/2021/
Electronic Design News ~ The search for extraterrestrial radio signals:
https://www.edn.com/the-search-for-extraterrestrial-radio-signals/
Technical Knowledge & Education:
Community of European Solar Radio Astronomers (CESRA) ~ VLA Measurements of
Faraday Rotation through a Coronal Mass Ejection Using Multiple Lines of Sight:
http://www.astro.gla.ac.uk/users/eduard/cesra/?p=2793
Cornell University ~ Galactic Radio Explorer: an all-sky monitor for bright radio bursts:
https://arxiv.org/abs/2101.09905
Online radio astronomy courses ~ audit for free or pay to receive certification:
The Radio Sky I: Science and Observations: https://www.edx.org/course/radio-sky-1
Plasma Physics: Introduction: https://www.edx.org/course/plasma-physics-introduction
History of Geo- and Space Sciences (HGGS) ~ A brief history of ball lightning
observations by scientists and trained professionals:
https://hgss.copernicus.org/articles/12/43/2021/
Hey, Mac, I want my Arecibo and I want it now: Cornell University ~ The Future Of The
Arecibo Observatory: The Next Generation Arecibo Telescope: https://arxiv.org/abs/2103.01367
Signal Hound ~ Understanding the Noise Floor on a Real-Time Spectrum Analyzer:
https://signalhound.com/content/tech-briefs/understanding-the-noise-floor-on-a-real-time-spectrum-analyzer/
9
US Naval Post Graduate School ~
The Mitigation of Radio Noise from External Sources at Radio Receiving Sites:
www.arrl.org/files/file/Technology/pdf/ExternalNoiseHandbook.pdf
The Mitigation of Radio Noise and Interference from On-Site Sources at Radio
Receiving Sites:
www.arrl.org/files/file/Technology/RFI%20Main%20Page/Naval_RFI_Handbook.pdf
University of Alaska Fairbanks ~ Space Weather Underground: https://sites.google.com/alaska.edu/swug/
Rhode & Schwarz ~ Making Better Oscilloscope Measurements: https://www.rohde-
schwarz.com/us/campaigns/rsa/icr/making-better-oscilloscope-measurements_253739.html
Community of European Solar Radio Astronomers (CESRA) ~ On the occurrence of type IV solar radio bursts in
the solar cycle 24 and their association with coronal mass ejections:
http://www.astro.gla.ac.uk/users/eduard/cesra/?p=2807
EDN ~ The math behind the Smith chart: https://www.edn.com/the-math-behind-the-
smith-chart/
Vice ~ Why Channel 37 Doesn’t Exist (And What It Has to Do With Aliens):
https://www.vice.com/en/article/dy8by7/why-channel-37-doesnt-exist-and-what-it-
has-to-do-with-aliens
Cornell University ~ A modern reconstruction of Carrington's observations (1853-1861):
https://arxiv.org/abs/2103.05353
CESRA ~ Analyzing the propagation of EUV waves and their connection with type II
radio bursts by combining numerical simulations and multi-instrument observations:
http://www.astro.gla.ac.uk/users/eduard/cesra/?p=2817
10Announcements ~ March-April 2021
SolFER Spring 2021 Meeting
https://solfer.umd.edu/events/conference.html
The SolFER DRIVE Science Center is announcing a web-based science meeting on Solar Flare Energy Release to
take place on May 24-26, 2021. The meeting is open to all scientists working on the topic. The meeting will
include invited talks, submitted oral talks as well as poster presentations and will provide substantial time for
informal scientific discussion. We encourage paper submissions that are based on remote and in situ
observational data as well as those based on theory and modeling. Extensive use will be made of Gather
meeting software to facilitate interactive poster sessions as well as informal discussion between meeting
participants. The meeting will be organized around the key scientific topics listed as follows:
✓ What mechanisms facilitate the fast release of magnetic energy in impulsive solar flares?
✓ What controls the onset of fast flare energy release?
✓ Why and how do flares transfer a large fraction of the released magnetic energy into energetic
electrons?
✓ What mechanism drives the energization of ions and the measured abundance enhancements of some
species during impulsive flares?
✓ What mechanisms control energetic particle transport in flares?
✓ How does reconnection heat plasma in flares and the small events (nanoflares) that may be responsible
for heating the corona?
More information on these scientific topics can be found on the SolFER website (solfer.umd.edu). Information
on abstract submission and more details on the daily timeline of the meeting are being developed for posting
on the website.
The SolFER science team also encourages community participation in the ongoing science discussion related to
flare energy release. A detailed calendar of working group meetings as well as the monthly webinar can be
found on the SolFER website (soler.umd.edu).
Radio Astronomy Group of the British Astronomical Association
The Radio Astronomy Group hosts bi-weekly Zoom Conferences
that include presentations and posters on various aspects of radio
astronomy. Scheduled conferences are listed below. The conferences are recorded and archived for viewing
later and have the following format:
18:15 UTC - Meeting room open for discussion
18:30 UTC - Introductions/notices
18:40 UTC - Main presentation
19:30 UTC - Q & A
19:50 UTC - Poster session, 10 min each. Brief presentation on current research and/or observations.
20:30 UTC - Finish
If you are interested in attending a conference or presenting for a main session or a poster session please
contact Paul Hearn at paul@hearn.org.uk. The Zoom link will be sent by email the day before the conference. A
11current list of conferences can be found at https://britastro.org/node/25793 and archives at
https://britastro.org/node/25798 . Conferences so far scheduled:
March 26th. RAGZoom2
Main Presentation: Radio Meteor Detection collaboration Project - John Berman
"A talk about what we are currently doing with data collected and where we may go in the future"
Poster sessions to be confirmed
April 9th. RAGZoom3
Main Presentation: SIDs and TIDs - the ups and downs of the ionosphere - Mark Edwards
Poster sessions to be confirmed
April 23rd. RAGZoom4
Main Presentation: Geomagnetism ~ Earth's Magnetic Field and the Sun - Whitham D. Reeve
Poster sessions to be confirmed
May 14th. RagZoom5
Main Presentation: Hydrogen-Line Observations and Instrumentation - Brian Coleman
Poster sessions to be confirmed
May 28th. RAGZoom6
Main Presentation: Current Observations from Astropeiler Stockert - Wolfgang Herrmann
Poster sessions to be confirmed
June 25th. RAGZoom7
Main Presentation: On the tricky question of Pulsars - Peter East OBE FREng
Poster sessions to be confirmed
July 23rd. RAGZoom8
Main Presentation: e-Callisto a Radio eye for Solar Activity - Christian Monstein
Poster sessions to be confirmed
12For Your Radio Astronomy Bookshelf
(Prices in USD)
Antenna Models for Electromagnetic Compatibility Analyses, C.W. Wang, T. Keech,.NTIA TM-13-489,
October 2012, Free download:
https://www.ntia.doc.gov/files/ntia/publications/antenna_models_report_tm-13-489.pdf
Fundamentals of Radio Astronomy Observational Methods, Marr, J.M.; Snell, R.L.; Kurtz, S.E.; 2016, CRC
Press, $110.00 (hardcover)
Galactic Radio Astronomy, Sofue, Y., ISBN 978-981-10-3444-2, Springer, $64.99 (hardcover)
Geomagnetism, Aeronomy and Space Weather – A Journey from Earth’s Core to the Sun, edited by M.
Mandea, M. Korte, A. Yau and E. Petrovsky, ISBN 978-1-1084-1848-5, 2020, 140 USD (hardback), Cambridge
University Press
Geomagnetic Disturbances Impacts on Power Systems: Risk Analysis and Mitigation Strategies, O. Sokolova,
N. Korovkin, M. Hayakawa, ISBN 978-03-676-8086-2, 170 USD (hardcover), 153 USD (eBook) , 2021, CRC Press
Handbook of Pulsar Astronomy, Lorimer, D.R.; Kramer, M.; ISBN 0-521-82823-6; 2005, Cambridge University
Press; $94.00, (hardcover)
Pulsar Astronomy, Lyne, A.G.; Graham-Smith, F. ISBN 0-521-32681-8, 1990, Cambridge University Press;
$47.95 (hardcover)
Radio Astronomy, 2nd Ed.; Kraus, J.D., ISBN 65-28593, 1986, McGraw-Hill, Inc. $49.95 (spiral bound)
The Cosmos: Astronomy in the New Millennium, 5th Ed., J. M. Pasachoff & A. Filippenko, ISBN: 978-1-1084-
3138-5, 2019, $80 (softcover), e-Book available, Cambridge University Press
Tools of Radio Astronomy, 6th Ed., Wilson, T.L.; Rohlfs, K.; Hüttemeister, S.; ISBN 3662517329, Springer,
$118.00 (hardcover)
13Please send all reports and observations to jacook@jacook.plus.com
BAA Radio Astronomy Section 2021 JANUARY
Solar activity through January was very low, with a short period mid-month of small B-class flares. The
strongest flare listed in the space weather bulletins was C1.4 peaking at 12:53UT on the 20th. Although well timed
for detection, it was not recorded on the very noisy signals typical at this time of year. The 23.4kHz signal has also
shown some large and rapid changes in signal strength towards the end of the month that have not helped.
MAGNETIC OBSERVATIONS
This chart shows the month’s activity recorded by Stuart Green. Despite the lack of flare activity, there
were some CMEs recorded in satellite images. These were from filament eruptions, and fairly mild. Combining
with coronal hole high speed winds they did result in some magnetic disturbances in the first half of the month.
14This recording by Nick Quinn shows the CME arrival just before midnight on the 5th, following a day of
mild disturbance from the CHHSS. Nick is using a fluxgate sensor buried 0.6m underground to reduce thermal
effects. The disturbance faded out during the 6th. The second CME / CHHSS combination arrived on the 11th, shown
here by Roger Blackwell:
There was clearly quite a strong shift in the magnetic field in the evening of the 11 th, although the turbulence
produced was fairly mild. The sensor is reset at midnight, hence the apparent break in the trace.
The magnetic disturbance starting on the 25th was entirely due to coronal hole effects, shown in this
recording by Nick Quinn:
There was a very mild disturbance during the morning, increasing through the afternoon with a large shift in the
east-west field just before midnight. The mild disturbance continued through the 26th, fading out in the morning
of the 27th. There were no reports of any effects on the 37.5kHz signal from these magnetic disturbances as they
were most active well after the winter sunset time.
Magnetic observations received from Roger Blackwell, Chris Bailey, Colin Clements. Stuart Green, Paul Hearn,
Andrew Thomas, Nick Quinn and John Cook.
QUADRANTID METEORS
Chris Bailey has continued his meteor recording with the GRAVES radar signal to catch the January
Quadrantids. His echo counts are shown in the chart on the next page:
15The peak in the morning of the 3rd is in good agreement with the details in the BAA handbook, with over
300 radar reflections being detected between 10 and 11UT. Good rates were also recorded over the entire six day
period shown. Some of the recordings are shown below. Note that the bright line underneath each echo is due to
interference.
16BAA Radio Astronomy Section 2021 FEBRUARY
February started with a very inactive sun, mostly without any sunspots. AR12804 became active in the
last week of the month, producing many small B-class flares. The strongest event of the month being a C3.9 flare
at 06:46UT on the 28th. This was far too early in the morning for us to detect, and so we have another month
without any recorded SIDs. Signals have been very noisy due to the low level of solar activity.
MAGNETIC OBSERVATIONS
The monthly magnetic summary from Stuart Green shows that February was a very active month, with
magnetic disturbances present on most days. The majority of the disturbance was due to the high speed wind
from coronal holes.
This recording by Nick Quinn shows quite a strong disturbance starting in the evening of the 6th and
continuing into the 7th. This faded out later in the afternoon, but there was a further brief disturbance in the
evening of the 8th.
Unusually, the disturbance on the 13th was at its strongest in the morning, fading out after midday. This is
shown in the recording by Roger Blackwell:
17A combination of multiple coronal holes as well as a possible glancing blow from a small CME led to the
magnetic disturbance starting on the 19th and running right through to the end of the month.
This recording by Paul Hearn shows a strong build-up of activity in the late afternoon of the 20th as the
effects of the southern polar coronal hole and equatorial coronal hole combine. These coronal holes were over
quite a large area, but were very patchy. The Earth-Sun geometry at this time of year allows easier access of the
solar wind into the Earth’s magnetosphere.
Activity reduced a little after 02UT on the 21st, shown in the following recording by Colin Clements:
18Nick Quinn’s recording shows a brief pulse of activity around 21UT on the 22nd, followed by more gentle
disturbances in the morning of the 23rd.
19The recording by Roger Blackwell shows a further period of active disturbance in the evening of the 24th,
with more gentle activity on the 25th. Mild disturbance continued through to the end of the month.
Andrew Thomas has combined the week’s magnetic activity into a single chart, shown above.
Magnetic observations received from Roger Blackwell, Colin Clements, Stuart Green, Paul Hearn, Nick Quinn,
Andrew Thomas and John cook.
METEOR OBSERVATIONS
Gordon Holmes, a new member, has sent in this recording made at the time of the widely seen fireball on
February 28th. Grid lines are at 16 minute intervals. The fireball images that I have seen were timed at 21:54UT,
about 10 minutes before the magnetic pulse recorded here. I have received no other recordings around this time.
I suspect that this might just be a coincidence, but include it here to invite any comments. Meteors have been
well documented producing VLF effects, but usually at frequencies lower that those used for SID detection. After
sunset the signals are far too random to show any connection.
Paul Hearn has started a series of zoom meetings for the radio astronomy section. The first of these proved
to be very popular and has led to a number of suggestions for topics to be covered in future meetings. A full
programme is available on our BAA website (URL on the heading of this summary), and is being updated as more
20dates are confirmed. If you are interested and able to join in, then please do follow the links shown there. I do not
have adequate equipment on this old XP PC, so I have had to take the back-seat for this. My thanks to Paul.
2122
SuperSID
Collaboration of Society
of Amateur Radio
Astronomers and
Stanford Solar Center
✓ Stanford provides data hosting, database programming, and maintains the SuperSID website
✓ Society of Amateur Radio Astronomers (SARA) sells the SuperSID monitors for 48 USD to amateur radio astronomers
and the funds are then used to support free distribution to students all over the world (image below as of Fall 2017)
✓
✓ Jonathan Pettingale at SARA is responsible for building and shipping the SuperSID monitor kits: SuperSID@radio-
astronomy.org
✓ SuperSID kits may be ordered through the SARA SuperSID webpage: http://radio-astronomy.org/node/210
✓ Questions about the SuperSID project may be directed to Steve Berl at Stanford: steveberl@gmail.com
✓ Jaap Akkerhuis at Stanford is responsible for the SuperSID software and SARA has provided financial support for his
efforts
✓ SuperSID website hosted by Stanford: http://solar-center.stanford.edu/SID/sidmonitor/
✓ SuperSID database: http://sid.stanford.edu/database-browser/
✓ The data is searchable by time, station, date, and multiple plots may be placed on the same graph for comparison.
✓
23For official use only
Monitor assigned: __________
Site name: ________________
Country: __________________
SuperSID Space Weather Monitor
Request Form
Your information here
Name of site/school (if an
institution):
Choose a site name:
(3-6 characters) No Spaces
Primary contact person:
Email:
Phone(s):
Primary Address: Name
School or Business
Street
Street
City State/Province
Country Postal Code
Shipping address, if Name
different: School or Business
Street
Street
City State/Province
Country Postal Code
Shipping phone number:
Latitude & longitude of site: Latitude: ____________________________ Longitude: ___________________________
I understand that neither Stanford nor the Society of Amateur Radio Astronomers is responsible for accidents
or injuries related to monitor use. I will assure that a surge protector and other lightning protection devices
are installed if necessary.
Signature: ____ Date:
I will need:
What Cost How many?
SuperSID distribution USB Power $48 (assembled)
USB Sound card 96 kHz sample rate (or $40 (optional)
provide this yourself)
Antenna wire (120 meters) $23 (optional) with connectors
(or you can provide this yourself) attached and tested
RG 58 Coax Cable (9 meters) $14 (optional) with connectors
(or provide this yourself) attached and tested
Shipping US $12 Canada & Mexico $40
all other $60
TOTAL $
24____ I have included a $ check (payable to SARA)
____ I will make payment thru www.paypal.com to treas@radio-astronomy.org
or
____ If you are a Minority-serving institution, in a Developing or economically deprived nation, and/or you are using
the monitor with students for educational purposes, you may qualify for obtaining a monitor at reduced or no cost. Check
here if you wish to apply for this designation. Then tell us how you want to use the SuperSID monitor. Include type of site,
number of students involved, whether public or private school, grade levels, etc. and describe your program. The goal of the
SuperSID project is to provide as many students with systems as possible. If you are able to pay for a system, even if you
qualify for a free one, please do so and help support our goal.
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
For more details on the Space Weather Monitor project, see: http://sid.stanford.edu
To set up a SuperSID monitor you will need:
1. Access to power and an antenna location that is relatively free of electric interference (could be
indoors or out)
2. A PC** with the following minimal specifications:
• A sound card that can record (sample) up to 96 kHz, or a USB port to connect such a sound
card (for North and South America)
▪ All other countries can use AC97 sound card with 48 kHz record (sample) rate.
Most computers made after 1997 will have AC97.
• Windows 2000 or more recent operating system
• 1 GHz Processer with 128 mb RAM
• Ethernet connection & internet browser (desirable, but not required)
• Standard keyboard, mouse, monitor, etc.
3. An inexpensive antenna that you build yourself. You’ll need about 120 meters (400 feet) of
insulated wire. Solid wire is easier to wind than stranded. Magnet wire will work but be more
fragile. You can use anything from #18 to #26 size wire. The antenna frame can be made of wood,
PVC pipe, or similar materials. We’ll provide instructions. You can purchase the wire from us or
obtain your own.
4. RG58 coax cable with a BNC connector at one end to run from the antenna to the SuperSID
receiver. 9 meters is recommended, but the length will depend on where you place the antenna.
You can purchase the coax from us or obtain your own.
5. Surge protector and other protection against a lightning strike
Return this form to: SuperSID@radio-astronomy.org
or mail to: SARA
Brian O’Rourke, SARA Treasurer
337 Meadow Ridge Rd,
Troy, VA 22974-3256
25Feature Articles
New Specialty Amplifier with Small Parabolic Antenna Advances Hydrogen Line Observing
By Stephen Tzikas, MS Chemical Engineering
Introduction
Small radio telescopes are frequently constructed by university students for the observations of the 21 cm
hydrogen line. Many skilled amateurs build such telescopes as do-it-yourself plans that have been available on
the internet for years. However, no ready-made affordable kits for easy assembly have been available until now.
Pablo Lewin of the Maury Lewin Astronomical Observatory in Glendora, California, and a member of the Society
of Amateur Radio Astronomers (SARA) followed the instructions on the internet for the construction of one of
these radio telescopes. The radio telescope was constructed for under $300. Discussion with SARA on
standardizing the supply of materials and the software requirements lead to the first ever “scope-in-a-box” for
any individual to purchase a ready-made hydrogen line telescope. The “scope-in-a-box system is based on the
article from rtl-sdr.com who developed the approach:
https://www.rtl-sdr.com/cheap-and-easy-hydrogen-line-radio-astronomy-with-a-rtl-sdr-wifi-parabolic-grid-dish-
lna-and-sdrsharp/
Pablo’s insight to help create the “scope-in-a-box” will help bring radio astronomy to the masses, who otherwise
might not have had the confidence to construct the telescope on their own. He implemented the instructions and
even improved on them by adding a bigger antenna and another low noise amplifier (wideband) in line with the
original one. A video of his set-up which is based on the same system noted at rtl-sdr.com can be seen at this link:
https://www.youtube.com/watch?v=jgTAw_SvH48
As one of the beta-testers of the “scope-in-a-box,” I had the opportunity to assemble the instrument, install the
software, follow the initial instructions, and finally evaluate the process and recommend improvements to the
instructions. The radio telescope can now be ordered from SARA for under $300 (SARA places the order on
Amazon.com for the consumer electronics and hardware required). It is an excellent way to learn and observe in
radio astronomy. The part I enjoyed the most was the hands-on experience I obtained through the scope’s easy
assembly and software use. It is that interactive practical experience that I discuss in this article. While optical
telescopes are fairly straight forward, radio telescopes require a little more familiarity with electronics. I hope
this article helps your adventure into hydrogen line observing. The SARA kit is a radio telescope with some simple
assembly and software installation. The scope-in-a-box allows one to learn about the working components of their
radio telescope.
Background
In 1951, Harvard scientists Ewen & Purcell were the first to detect the 21cm line (at 1420 MHz). This allowed the
measurement of the galactic rotation curve, as this radiation from hydrogen penetrates galactic dust clouds. By
1952 the first radio charts of the neutral hydrogen in the galaxy were plotted, and the spiral structure of the galaxy
was revealed. This radiation is generated from a transition between two energy levels of the electron spin in the
neutral hydrogen 1s ground state. This galactic emission was first predicted by H. van de Hulst in 1945. This built
on earlier discoveries in the 1930s of radio emissions from the center of our galaxy, and that they could be
associated with emission lines in the radio part of the electromagnetic spectrum. Hulst predicted this frequency
26to be at 1420.4058 MHz. For those who attend the Eastern summer conference of SARA at the Greenbank
Observatory, the original horn antenna used by Ewen and Purcell can be found on campus in front of the classic
1960s architecture of the Jansky Laboratory. For the artist, it makes a perfect scene for a sketch or oil painting.
The Scope-In-A-Box
For those who order the scope-in-a-box, they will receive the following main components:
Hardware
• Antenna with feedhorn and reflector
• Tripod and mount
• Rabbit Ears Antenna for testing
Electronics
• RTLSDR and connecting cable for laptop.
• SAWBird LNA, and the adapter between Feedhorn and SWABird LNA
• 50 Ohm Terminator
• A few miscellaneous parts (of larger packages) not required for the scope.
Software
• Software on the SARA thumb-drive
Hardware Assembly
The scope-in-a-box comes with a Premiertek Outdoor 2.4 GHz 24 DBI Directional High Gain N-Type Female
Aluminum Die Cast Reflector Grid Parabolic Antenna (ANT-GRID-24DBI) valued at about $85. It has a height of
23.6” and a width of 41.7”. The Beamwidth/Horizontal is 14º, while the Beamwidth/Vertical is 10º. Those who
have purchased other radio astronomy telescope kits in the past will notice this antenna is different. It is not the
parabolic dish of an IBT, nor the loop antenna of a SuperSID, nor the dipole antenna of a Radio Jove kit. To help
put this in perspective, antennas are classified by their physical structure and functionality. Some types of
antennas include, but are not limited to:
• Wire Antennas: Dipole, Helix, Whip, and Loop for appliances, buildings and conveyances
• Reflector Antennas: Parabolic for microwave transmission, satellite tracking and radio astronomy
• Aperture Antennas: Horn antennas for aircraft and spacecraft
• Microstrip Antennas: Metallic patch/strip for conveyances and mobile phones
• Array Antennas: Yagi antennas for high gain applications with control of the radiation pattern
• Lens Antennas: Lens for very high frequency applications
Notice that the parabolic grid antenna of the scope-in-a-box also comes with a feedhorn. A feedhorn is a horn
antenna. It receives the reflected waves from the parabolic grid. Some key functions of a feedhorn include
supporting a specific frequency range; supporting a particular type of polarization based on its waveguide shape;
providing a certain amount of gain; and offering flange compatibility to connect the feedhorn to a low noise band
(or block) converter of frequencies, which can convert to another frequency for input to a receiver.
Finally for hardware, the tripod assemby consists of a Model SKY6016 tripod/base mount with level and compass,
3 feet tall, costing about $43. The antenna, tripod, and mount are all metal.
27Electronics Assembly
The electronics parts in the scope-in-a-box consists of:
• Nooelec SAWbird+ H1 – Premium Saw Filter & Cascaded Ultra-Low Noise Amplifier (LNA) Module for
Hydrogen Line (21cm) Applications 1420MHz Center Frequency. Designed for Software Defined Radio
(SDR), about $45.
• RTL-SDR Blog V3 R820T2 RTL2832U 1PPM TCXO HF Bias Tee SMA Software Defined Radio with Dipole
Antenna Kit (this is the dongle and rabbit ears antenna), about $38.
• USB 3.0 Extension Cable 10FT Type A Male to female Extension Cord AINOPE High Data Transfer
Compatible with USB Keyboard, Flash Drive, Hard Drive, about $10.
• Maxmoral N Type Male to SMA Male convertor Wi-Fi Adaptor Connector, about $7.
• DHT Electronics RF Coaxial Connector Adapter SMA Male Coaxial Termination Loads 1W DC – 3.0GHz 50
Ohm, about $6.
The NooElec LNA and filter is specifically designed for amateur radio astronomers, and to be used with the RTL-
SDR dongle for the reception of hydrogen line. This LNA has a high gain and a good RF filter for reducing
interference. It comes with a power LED indicator.
The RTL-SDR dongle comes in a multipurpose antenna set. This smaller whip antenna is used for testing the dongle
and software installation of the scope-in-a-box. Beside hydrogen line observing, the RTL-SDR dongle can be used
for many other amateur ham radio applications associated with meteor scatter monitoring; satellite and weather
balloon reception; public safety radio; and general radio scanning. It has a frequency range of 500 KHz to 1.7 GHz.
It has up to 3.2 MHz of instantaneous bandwidth and is 2.4 MHz stable. It is safe for travel through airport
scanners. X-rays don't create currents in the circuitry, especially if not powered. RTL is short for RTL2832U. It is
a Realtek RTL2832U chipset that is popular and can be used for wideband Software Defined Radio (SDR) receivers.
Such devices known as RTL-SDR dongles. It takes radio frequency signals and converts them to audio frequency.
Hence the scope-in-a-box picks up many FM radio stations. The SDR software performs all of the digital signal
processing,
In electronics, there are many types of connectors. The N type male to SMA male connector is used in radio
frequency electronics. N connectors are named after Paul Neill of Bell Labs. It’s a threaded, weatherproof
connector for coaxial cables. SMA connectors stand for subminiature version A. They too are used to connect
coaxial cables and have a screw-type coupling mechanism.
The 50 ohm terminator can be placed on unused coaxial ports to prevent the RF signal from reflecting. It is used
in the calibration process for the scope-in-a-box.
SDRSharp Software Installation and Calibration
The scope-in-a-box uses an SDR receiver. As the name implies, it is digital based rather than analog based. This
software must take the analog signals received from the sky and convert it to digital. It accomplishes this by
converting the electrical signals to binary format. The continuous analog signal is sampled at regular intervals and
assigned a discrete string of bits, that is, the binary digits. The actual creation is based on two voltage bands. One
is near a reference value (ground or zero volts). The other near the supply voltage. These represent zero and one.
For example, when a microcontroller is powered by 5 volts, it recognizes 0 volts as binary 0, and 5 volts as binary
1. The instrument that converts from analog to digital is called an Analog to Digital Converter (ADC). It takes an
28analog voltage on a pin and converts it to a digital format. Since the conversion quantizes the input, it introduces
a small error. ADC performance is based on its bandwidth (sampling rate) and signal-to-noise ratio (SNR). The
SNR is affected by resolution, linearity, accuracy, aliasing, and jitter (timing errors).
The new scope-in-a-box kit represents the latest effort to bring a part of radio astronomy to the masses. It is
affordable, easy to assemble, and will offer hours enjoyment and a launch pad for other radio astronomy activities.
29“Scope in a Box” First Experience and Some Enhancements.
Alberto Sagüés*, KA4MTO, Lutz, Florida
Contact:
Sharing the Experience
I wrote this to share some of my first, getting-acquainted steps in amateur radio astronomy, which is being
revolutionized by the availability of powerful affordable instrumentation and software. Last December Dennis
Farr, to whom we owe so much in the Tampa area for promoting astronomy both optical and radio, alerted me
that the Society of Amateur Radio Astronomers (SARA) had facilitated things by putting together a “Scope in a
box” radio telescope kit for beginners. It did not take much to persuade me to try it, and I ordered one. Here I
describe my experience with putting the Scope together, the “first light” try, an enhancement to motorize the
antenna, and my first (I think quite lucky) attempt at using the Scope to map the sky on the hydrogen 1.4 GHz line.
I hope that this narrative will get others equally animated to try the Scope, and variations like illustrated here.
The Kit
The site https://www.rtl-sdr.com/cheap-and-easy-hydrogen-line-radio-astronomy-with-a-rtl-sdr-wifi-
parabolic-grid-dish-lna-and-sdrsharp/ describes in detail what the Scope is based on, what it does, and how to
download and install the (free) software for it. The version sold at the time included the following (I understand
that now they supply with the kit a thumb drive with software/instructions):
• RTL-SDR V3 (a Software Defined Radio (SDR) USB dongle made by RTL)
• Type N to SMA adapters (coaxial cable adapters; one large-to-small and one small-to-small)
• 50 ohm termination loads SMA connectors (50 ohm resistors that screw in at the coaxial cable connector)
• Nooelec SAWbird LNA with filter for H1. This is a Low Noise Amplifier (LNA) module with a bandpass filter
around the 1420 MHz frequency of the H1 signal, terminated by coax connectors.
• 10ft USB Extension cable (low loss USB-3 cable that connects between the SDR and the computer)
• Tripod for antenna (a sturdy steel/plastic tripod)
• 2.4GHz Directional High-Gain Antenna (about 1m wide parabolic antenna with output via a short Type N
coax cable).
The items arrived after just a few days, well packed with no shortages or damage.
Assembly
I assembled the antenna first; it was straightforward. The dish hardware includes metric stainless steel
fasteners that will not rust. The dish weighs about 5 lb. Next I assembled the tripod. It has a ~ 2-inch diameter
plain steel pipe that fits inside a plastic base that in turn has three plain steel legs. In my unit the plastic base hole
was too tight to fit the pipe all the way in, so I used a rasp to enlarge the hole. It goes in further now, allowing for
adequate tightening with a provided set screw lever. The antenna is attached to the pipe with provided U-braces;
I enlarged a couple of brace holes a bit with a small file for easier fit but overall, mechanical complication in
assembly was minimal. The tripod legs open or close with no effort; if you want them not to fold back in you can
add in jamming screws, which I did later.
30Electrical assembly was straightforward too. The large-to-small coax adapter is connected between the
thick antenna coax and the LNA input. The small-to-small coax adapter goes between the LNA output and the SDR,
and the USB-3 cable goes between the SDR and the computer. Be prepared to periodically undo the connection
between the LNA and the antenna-side adapter to screw in the LNA input one of the 50 ohm termination loads
for calibration.
Next, I did software download and installation following the instructions in the website. Remarkably, all
installations worked on the first try. Do patiently follow the instructions including those in the Quickstart Guide
for the SDR; it is easy to inadvertently skip over some of the steps. The computer I used first was a Microsoft
Surface Pro 2 with Windows 10.
First Light
For my first “light” test I took the antenna outdoors and pointed it to the zenith as indicated in the Scope
description website. I temporarily disconnected the antenna from the LNA and connected the 50 ohm terminator
to the LNA input. I followed then the website instructions under “Receiving and Averaging the Hydrogen line FFT”.
During the first steps, don’t forget to click in the “Offset Tuning” box in the screen, which according to the
instructions will “enable the bias tee via the V3 driver hack”. Translation for non-geeks: The USB3 cable powers
the SDR dongle, and the SDR dongle passes some of the USB power up to the LNA with a circuit called the “bias
tee”, so the LNA can run too. That function is software-controlled by a plug-in called “V3” that you download
during installation and is activated by clicking in “Offset Tuning”. When you do that, you will see a white LED turn
on in the LNA, indicating that it is getting power. If the LED is dark, the LNA is not getting power; check to make
sure you followed correctly the turn-on steps.
After I tuned the SDR to 1,420.000 MHz and got to the IF Average part of the procedure, I departed from
their recommended setting (which would average the signal over seven long minutes) to something that renewed
screens much faster so you can see results from changes you made after a few seconds: FFT Resolution=1024,
Intermediate average=10, Gain = 274, Level=973, and Dynamic Averaging = 27040. Then, I clicked in Window,
pressed Background and waited a couple renewal cycles. First times the resulting IF average window tended to be
either all blue or all black. I needed then to change the Gain setting up or down until the line graph showed within
the screen range. The correct graph looked like a horizontal or moderately sloping line usually with small twists
near the left and right ends.
Now it was time to unscrew the 50 ohm terminator and reconnect the antenna coax. The result after a
couple screen renewals is shown in Figure1. The H1 line was clearly visible as the blip a bit to the right of the 1420
MHz marker. The display was a bit noisy due to the short time averaging, and the spike near 1421 MHz was an
artifact, but otherwise functionality looked good. Checking Stellarium (open source software recommended in
the instructions) I found that at the time of the test the Galaxy’s bright “band” was a bit off the zenith, being
brighter some 30-40 degrees to the west. Thus I tilted the antenna against a stool a bit in that direction, with the
result shown in Figure 2. The line was a bit more substantial, as expected. The results were promising so I moved
on the next stage: motorized scanning of the sky.
31Figure 1 – Antenna to Zenith. Figure 2 – Antenna tilted to a brighter zone of the
Galaxy.
32Motorized Altitude Scanning
Having established that the system was operational, the next idea was to motorize the antenna so it would
rapidly scan in the N-S direction, and to repeat that at intervals during the day so as to record the scans at various
right ascensions, thus getting a 2D H1 map of the sky from which a grayscale image of the galaxy could be
constructed.
Note: DO NOT attempt anything hardware-related like this unless you are thoroughly familiar and
proficient with mechanical and electric safety practice. That includes, but is not limited to,
implementing grounding/isolation of motor, antenna and cables as appropriate; avoiding
accidental contact of the antenna with power lines; and adequate lightning protection. Otherwise
there is risk of deadly electric shock, and serious computer and other property damage.
To achieve the N-S rotation I revived a 50-year old TV antenna rotor that I had kept in the attic for the last
few decades, waiting for just this occasion. It is a genuine Alliance Tenna-Rotor (R) Model U-100 complete with its
1960’s style control box. The motor is actually a 1 RPM servo with position encoded at 10 degree intervals by a
cam and spring contacts. Control logic is fully electromechanical via a clunky solenoid and lots of cleverness. The
motor is synchronous and operated at about 30 V, 60 Hz, powered by the wall socket via a transformer. The control
box back-to-back electrolytic capacitors used to get the right phase shift in the motor coils were dead, so I had to
replace those. Once that was done and the motor gears and bushings were properly cleaned and re-lubricated,
the system worked beautifully.
The rotor was designed to operate in azimuth, so for altitude I turned it on its side and made a bracket to
hold it that way on top of the tripod pipe. Then I slipped inside the shaft opening an approximately 1x1 inch square
steel channel. The channel protruded on two sides; on one side I attached the antenna bracket and on the other
a 6 lb counterweight made of a surplus motor flywheel, positioned to balance by adjusting radial distance on a
threaded rod. The arrangement is shown in Figure 3. The adjusted system was in good static balance so on
rotation the motor did not need to overcome any large torque on top of friction, which was not much. Center of
gravity was on the vertical pipe. I attached the tripod to a board with wheel casters for easy rolling in and out the
garage.
At first, I did not know how to prevent the thick coax from twisting back and forth (and eventually failing
by fatigue) as the motor rotated. On correspondence with the very helpful SARA team, I followed the great idea
from Pablo Lewin, WA6RSV to make a one-time bend of the coax so it met the LNA-SDR dongle tandem near the
axis of rotation. Thus, the small residual motion is handled by the much thinner and more flexible USB cable,
loosely wrapped ½ turn around the axis. This is shown in Figure 4.
33You can also read
